Directional antenna system



H. r-:. HOLLM ANN v ,227,088 DIRECTIONAL ANTENNA SYSTEM Filed April 19, 1937 INVENTOR IMMS mew you/14.4w

ATroRNEY Patented Dec. 31, 1 940 uni-tea STATES PATENT orrice DmEGTIONAL ANTENNA SYSTEM tion of Germany Application April. 19, 1931, Serial No. 137,690 In Germany May 11, 1936 aciaims. (01'. 250-11 This. invention is concerned with an antenna array, which combines. reduceddimensions with marked concentration of the beam energy.

In earlier publicationsare illustrated antennae which. consist. of alvertical. conductor atv the top end. of, which is. attacheda brush or bunch of wireswhich-are shortcompared with the Wavelength However, these wires evidently serve only, as, capacity-surfaces intended to load the antennae. It. isvalso known that a linear or straight antenna excited inharmonic wavessends out ,various radiation lobes the median lines of which according, to their ordinal number of the harmonics setup and excited on the antenna, present.differentanglesiin.reference to the antenna axis... Thisphenornenonhas led'to the constructionof a V-shaped antenna of the. kind shown forinstance, by way of examplein Fig. 1 anddescribedihsome detaill in United States PatentNo,1,974,387,grantediSeptember 18, 1934,

toPhilipS; Carter. FigureZshows an embodiment ,of my invention while Figure 3- sho-ws a modification usinglareflector and Figure 4 shows anarrangement of "my invention for radio-beacon of inclinationof the twoantennae in reference-to eachother, amounts vto..,2 36=72f, theradiation maXi-rna .due-tothetwo limbs will overlap inlthe "direction of tthe,bisector of the angle so that a more marked. concentration ofthe energy beam is ,obtainedthanwhatiwould resultfrom each.

of the, .twoantennae. Inthepresence offexciting 45 conditions diifs'srent from, those .of the example,

that is to say, for other values of the ratio antenna length 1: wavelength A, the angles which should be adopted are as follows, in order that exact coveringof, the radiation lobes that are richest in energy maybe secured:

This fact, which isvquite Well known in the art, 5 v is utilizedin the. present invention with theresult degrees."

that a further concentration of the energy beam is obtained by mounting an entire row of linear antennae capable of self-excitation, having dissimilar lengths I and relatively staggered or displaced angles 0: corresponding to each case,'fan fashion, preferably in a single plane. What thus results is an array of directive antennae lookin like the one shown in Fig. 2, the length of the constituent branches as well as the angles formed between the latter fulfilling the above-conditions ancldata. In'the lightof the above explanations, it will be readily understood that the radiation crests of all of the constituent antenna branches willcoincide in theb'isect'or symmetry plane and that this, of necessity, will enhance the sharpness of directivity of the ensuing aggregate diagram.

Fundamentally speaking, the radiation of the described system, just like that of a V-shaped antenna is uniform forward and backwards, that is to s'ay,'in the direction of the bisector of the angle, as well as inthe sense ofan extension of the bisector line beyondthe apex of the angle. In order to insure aunilateral directional diagram of the kind generally required in practice, it is possible to'mount posteriorly of the-radiator system proper,-a suitablerefiector system in a way'known from the prior art so that the radiation vectorsin the sense of'the bisector will add, while in the opposite sense they will mutually cancel, If the distance between the antenna systemand the reflector system required to this end, which, according to the exciting phase of the reflector must'be equal to different multiples oft/4, is less than the longest antenna branches, with both systems facing the same direction, the antennae of the reflector system will collide with those of the radiator system.- In order to avoid this, the reflector system may be reversed so that the vbranches of the radiator system in the sense of'the desiredradiation are inclined in reference to each other, while those of the reflector system are directed" oppositely. In this manner there results a combined antenna structure presenting a unilateral'directional characteristic according to the scheme indicated in Fig. 3 where A is the radiator or antenna system and R the reflector system.

Conjointly with the concentration of the beam in the horizontal plane, there is eifected also an energy concentration in the vertical plane, and this may be increased bythe disposition of several fan antennae fed. in phase and superposed with a spacingof M2.

Thefan antenna, finally, may be employed as a twin type radio beacon or ra ge n a v ry imp manner by periodically varying the excitation of the two fan halves either in amplitude or phase at the rhythm of the letters (1-11. or in some other rapid succession. As has been indicated in Fig- 3, one of the two halves will then predominate and accordingly there will be a shift of the directional diagram either towards the right (II) or towards the left (I) in reference to the plane of symmetry, while the symmetry plane itself is preserved as the plane of equal radiation energy. In order that unilateral directive radiation may be preserved also in the twin radio range, a reflector system may be used the two halves -of which, with a View to boosting the twin action, are changed over at the same rhythm as the aerial itself either in intensity or in phase.

Fig. 4 shows such an arrangement in more detail. The antenna system A is fed by way of the energy feeder line L, L'- Interposed in the line are by-pass lines, in the shape of U-shaped clips or bows U, U, and these by the agency of the keying device T, T are alternately short circuited. Instead of the said bows or loops, it would also be feasible to insert other impedances in one or in both wires, say, ohmic resistances W as indicated in Figure 5 where the portion between dotted lines XX-and YY is to be substituted for the portion between similarly identified dotted lines in Figure 4. Inductive impedances may likewise be used if desired. The impedances are alternately short circuited at therhythm of the signals by the aid of the switches T and T. If desired, the impedances may be omitted so that an open circuit is alternately produced in first one line and then the other. Unilateral directivity is obtainable by mounting a reflector wall R made of metal sheet or gauze as known in the prior art. However, it is also feasible to use a reflector system of the kind shown in Fig. 3 in which the feed of the twohalves is varied either as regards amplitude by series connected resistances or reactances or else in reference to phase by means of by-pass leads U in synchronism with the main antenna.

What is claimed is:

1- An antenna system comprising a two-conductor transmission line, a plurality of V-antennae of different lengths having a common bisector and a common apex, each V-antenna comprising a pair of wires angularly disposed with respect to each other and connected to said line in such manner that opposite instantaneous polarties are produced on corresponding points of the wires of the V, the angles of said Vs being 1 different and depending upon the length of the wires of the V whereby each V produces maximum radiation along the plane of the'common bisector.

2. A directional antenna comprising a pair of substantially equal conductors angularly disposed with respect to each other, each of a length including a plurality of half wavelengths, another similar pair of such angularly disposed linear conductors, the wires of said first pair being of different length from the wires of said. second pair, the end of each wire of one pair being directly connected to the end of wire of the other pair, the angle formed by the conductors of one pair being coaxially arranged with respect to the angle of the other pair, whereby there is a common bisector, and means for exciting the radiators of each pair in phase opposition whereby standing waves of opposite instantaneous polarity are formed thereon, whereby radiant action of each pair is predominantly along the plane of the common bisector of the angles formed by the conductors.

3. An antenna system comprising a two-conductor transmission line, a plurality of V antennae of different lengths having a common bisector and a common apex, each V antenna comprising a pair of wires angularly disposed with respect to each other and connected to said line, the angles between the wires of each pair being inversely proportional to their length whereby maximum radiation along the plane of the common bisector is produced- 4. An antenna system including radiator and reflection elements, each of said elements comprising a plurality of V antennae of difierent lengths having a common bisector and a common apex, each V antenna comprising a pair of wires angularly disposed with respect to each other, the angles between each pair of wires being inversely proportional to their length, the common bisectors of each of said elements being co-axial and the open ends of each of said elements facing in opposite directions.

5. A directional antenna system comprising a pair of substantially equal length conductors angularly disposed with respect to each other, each of a length including a plurality of half wave lengths, another similar pair of angularly disposedlinear conductors, the wires of said first pair being of a different length from the wires of said second pair, the end of each Wire of one pair being directly connected to the end of a wire of the other pair, the angle formed by the conductors of one pair being co-axially arranged with respect to the angle formed by the conductors of the other pair whereby there is a common bisector, and means for exciting in a periodically alternating relationship the radiators of each pair whereby a plane of equal radiation from the wires of each pair is formed extending pre-@ dominantly along the plane of the common bisector of the angles formed by the conductors.

6. A radio beacon antenna comprising a plurality of pairs of antenna conductors, the length of each pair of conductors being different, said conductors being disposed fan-wise in a single horizontal plane, corresponding conductors of each pair connected at the same point to a twoconductor transmission line, and meansfor energizing in a periodically alternating relationship the conductors of said line whereby a zone of substantially equal radiated energy is produced along a line forming a bisector of the fan formed by said pairs of wires.

'7. A beacon antenna system comprising a twoconductor transmission line, a plurality of V antennae of diiferent lengths having a common bisector and a common apex, each V antenna comprising a pair of wires angularly disposed with respect to each other and connected to said line, the angles between the wires of each pair being inversely proportional to their length, and means for energizing in a periodically varying relationship the wires on each side of said common bisector whereby an area of substantially equal radiation is formed along the plane of the common bisector of the angles formed by the said pairs of wires.

8. An antenna system including radiator and reflection elements, each of said elements comprising a plurality of V antennae of different lengths having a common bisector and a common apex, each V antenna comprising a pair of wires angularly disposed with respect to each other, the angles between each pair of wires being inversely sectors of each of said elements being co-axial and the open ends of each of said elements facing in opposite directions, and means for energizing in a periodically varying relationship all of the wires ofi each side of said common bisectors 5 whereby a zone of substantially equal radiation is produced along the plane of said common bisectors.

HANS ERICH HOLLMANN. 

